This battery life calculator estimates how long a battery will last, based on nominal battery capacity and the average current that a load is drawing from it. Battery capacity is typically measured in Amp-hours (Ah) or milliamp-hours (mAh), although Watt-hours (Wh) is occasionally used. You can convert Watt-hours to Amp-hours by dividing by the battery’s nominal voltage (V) as follows: Ah = Wh / V An Amp-hour, also denoted as an Ampere-hour, is a measure of charge and equates to current flow over time. One Amp-hour is equal to one amp of continuous current flow for one hour. A milliamp-hour, or milliampere-hour, is one thousandth of an amp-hour, therefore a 1000 mAh battery would be equal to a 1 Ah battery. The results are estimates only; the actual results will vary with battery condition, age, temperature, discharge rate, and other factors. The predicted results will best represent actual results when using new, high-quality cells at room temperature when the estimated run time is between 1 hour and 1 year.